The game, as American politicos like to say, did not change Wednesday night, as the race for the White House entered the blast furnace of one-on-one debates.

But depending on how American voters absorb the heft of this crucial first encounter in Denver, the U.S. election may actually be back in play.

Showing a real-time liveliness that has largely eluded him through 18 awkward months on the campaign trail, Republican standard-bearer Mitt Romney brought the A-game nobody was quite sure he had.

Written off by much of the American media as a long shot, Romney had everything to prove in this, the first of three debates that will sharpen a bitterly divided country as it enters the home-stretch to Nov. 6.

It was expected to come in the form of “zingers.” And while there were a few — “trickle-down government” was the go-to rhetorical device, as Romney made the case for replacing Barack Obama — it was more the sheer comfort level of the former Massachusetts governor that carried the night.

Obama, by contrast, played the debate with extreme caution, maintaining a calm, professorial demeanour and avoiding several obvious counterattacks as he wandered through the policy weeds of the past four years.

The president’s performance was that of a front-runner protecting a lead. A rusty front-runner, even, this being his first unscripted, head-to-head encounter since 2008.

For the instant-opinion commentariat, there was no question — Romney won on points, and plenty of them.

A flurry of instant polls also backed that impression, including a CBS News survey of uncommitted voters, 46 per cent of whom picked Romney as the winner, compared to 22 per cent for Obama and 32 per cent calling it a tie.

Moderator Jim Lehrer led with a light touch, leaving the candidates ample room to roam across the full spectrum of front-line domestic issues, from economic growth and jobs to government regulation to the country’s staggering $16-trillion debt and what it connotes for the fraying American social safety net.

Romney tacked left on at least two of those fronts, hammering Obama over the Dodd-Frank financial regulations for “unintended consequences” of designating five banks “too big to fail.”

The result, said Romney, added up to “the biggest kiss to New York banks I’ve ever seen.”

On the debt question, Romney and Obama traded sharp rejoinders over the GOP plan, with the president attacking Romney’s proposals to cut taxes and bolster military spending as “math” that leaves all Americans guessing.

Romney countered that his plan guarantees no net addition to the U.S. budget deficit — a more centrist stance than he has previously shown and one certain to be vetted ferociously by media fact-checkers everywhere.

On America’s beloved yet financially endangered entitlement programs, Romney stressed that the changes he envisions won’t have any effect on “retirees or near-retirees.” Obama shot back that “if you’re 54 or 55, you might want to listen,” proceeding to spell out the implications of a voucher system that would effectively cap benefits for working Americans as they shift toward retirement.

What was striking, in the at times wonkish exchange of competing numbers and visions, was how little Obama made of Romney’s Achilles heel — the widely held perception of the GOP challenger as an out-of-touch quarter-billionaire with almost no sense of the struggles of everyday Americans.

Obama left unspoken Bain Capital, offshore havens and the multiple years of tax returns Romney has yet to disclose. The omissions were picked up instantly on Twitter, where a ferocious partisan duel played out in real-time.

Romney, by contrast, was the aggressor, at one point attacking Obama during an exchange on plans for education reform, saying the president is not “entitled” to his own facts.

“You’re entitled, Mr. President, to your own airplane and your own house, but not to your own facts,” said Romney. “I’m not going to cut education funding. I don’t have any plan to cut education funding.”

Romney also found a way to work Sesame Street into the equation of federal spending versus borrowing more from China. “I’m sorry, Jim,” he told moderator Lehrer, “I’m gonna stop the subsidy to PBS. I’m gonna stop other things. I like PBS, I like Big Bird, I actually like you, too.”

The question, for many months now, has been whether Americans like Romney. Or, if not like, at least bring themselves to trust his way beyond the downward slope of hope.

To that end, Romney made this night all about the American middle class — a recurring phrase throughout the debate. One of his attack lines went so far as to describe Obama’s economic leadership as a de facto tax on working Americans.

“Middle income Americans have seen their income come down by $4,300,” said Romney. “This is a tax in and of itself. I will call it the economy tax.”

What Americans will make of it remains to be seen. But immediate reaction late Wednesday broke evenly between praise for Romney and befuddlement at Obama’s perceived lack of passion. Even former White House adviser James Carville acknowledged, “Obama didn’t bring his A-game.”

Republicans, by contrast — so starved for joy since late August, when their convention ended with the widely ridiculed spectacle of Clint Eastwood browbeating an empty chair — went into an enthusiastic frenzy.

New Jersey’s Chris Christie, a prominent GOP surrogate, typified the drumbeat, saying the debate “changed the trajectory of the race.”

A testy David Axelrod, the top voice on Team Obama, shrugged it all away, telling reporters, “Let’s not get carried away with the drama of the moment.”

Yet this wasn’t just a rare sour note for the Obama camp, it was the first they’ve known in a campaign marked by gift upon gift in the form of self-inflicted wounds by their Republican opponents.